1. Field of the Invention
The present invention relates to a substrate treatment method for improving roughness of a pattern mask.
2. Description of the Related Art
Due to the wave properties of light applied to a resist film on a wafer during exposure processing, variation in measured dimension called LWR (Line Width Roughness) occurs in a resist pattern formed after development. If a base film is etched using the resist film having the rough pattern as described above as a mask, the etching shape is affected by the roughness, with the result that a circuit pattern formed by the etching becomes rough in shape and possibly fails to manufacture a semiconductor device with a desired quality.
Hence, it is discussed to expose the resist pattern in a solvent atmosphere to swell and dissolve its surface to thereby smooth the surface of the resist pattern. For example, Japanese Patent Publication No. 4343018 describes, as an apparatus performing such treatment, a substrate treatment apparatus which includes a chuck sucking the wafer, a nozzle supplying a vaporized solvent from above the wafer, a moving mechanism moving the nozzle along a radial direction of the wafer, and a cup body surrounding the side circumference of the wafer and exhausting the inside thereof. However, provision of the cup body and the moving mechanism for the nozzle in the substrate treatment apparatus leads to an increase in footprint of the substrate treatment apparatus and an increase in manufacturing cost of the substrate treatment apparatus.
Hence, it is discussed to improve the roughness of the resist pattern using a substrate treatment apparatus including a treatment container storing a wafer, a discharge port provided at the treatment container, and a supply mechanism supplying a vaporized solvent from the discharge port. However, a problem of the substrate treatment apparatus is that it is difficult to perform treatment with high uniformity within the wafer.
Concretely describing the problem, the vaporized solvent flows on the wafer surface while adhering to the wafer, so that the supply amount of the solvent is larger near the discharge port than at a position away from the discharge port. Further, variation in flow speed of the vaporized solvent occurs within the wafer due to the arrangement of the discharge port and an exhaust port provided at the treatment container to cause a difference in concentration distribution and a place where the proportion of molecules of the solvent colliding with the wafer is higher. This possibly makes the resist pattern excessively swell to fall down or dissolve. In particular, when the line width of the resist pattern is made smaller in order to form a fine circuit pattern in the base film, the ratio of a thickness area where the solvent permeates to the thickness of the pattern becomes larger, and therefore the falling and dissolution of the pattern are thought to become likely to occur. On the other hand, at the position of the wafer away from the discharge port and at a position where the proportion of collision is small due to the variation in flow speed, the solvent cannot sufficiently eliminate in some cases the roughness of the resist pattern because the supply amount is small.
Japanese Patent Publication No. 4343018 does not describe the method to solve the above-described problem. Further, Japanese Patent Publication No. 4328667 describes a substrate treatment apparatus which supplies a vaporized solvent from a nozzle but does not describe the method to solve the problem.